Described below are a method, a radio system, a base station, and a computer program distribution medium.
Cellular operators may nowadays offer a local IP (Internet Protocol) connectivity within a certain area (local IP breakout) without roaming, with limited user mobility and IP session continuation being an alternative to the ordinary cellular packet data services with roaming and global mobility support. Such local IP connectivity may be provided within a local zone in a city center or any limited geographical area, an enterprise network or a home where radio coverage is available. In minimum, this kind of local IP breakout can be provided using one radio cell/base station and it may be expanded to a wide radio coverage area in the operator's nation wide domain (PLMN). For example, LTE/SAE (Long Term Evolution/System Architecture Evolution) service with roaming, and global/Inter Radio Access mobility with IP session continuation may be overlapping and may share the same cells/base stations that provide the local IP breakout service.
Network access to ordinary cellular packet data services is enabled e.g. in LTE/SAE via the cellular operator's core network that provides global roaming and mobility support. Normally UE (User Equipment, Mobile terminal) is connected to the radio network, such as E-UTRAN (Enhanced universal terrestrial radio access network) in the LTE/SAE of this example, in a way that a SAE Gateway that is located in the core network provides an IP point of attachment to the UE. The selection of this gateway takes place during an Initial Attach procedure when the UE is also authenticated and authorized to use the network services. The SAE Gateway can be selected either from the visited PLMN (Public Mobile Network) or the UE's home PLMN, depending on the roaming agreement between the operators. If a SAE Gateway is selected from the visited PLMN, a “local breakout” with roaming is in question.
In order to enable more local IP breakout services, a public mobile network gateway element, such as a SAE Gateway element, is required e.g. in the customer premises, home, office, or otherwise the local traffic has to be routed all the way to a centralized public mobile network gateway in the operator's premises and then back to the customer's infrastructure. One of the problems related to the known solutions is that the user data has to be traversed via the centralized public mobile network gateway, such as the SAE Gateway. Non-optimal user data routing increases transfer delays in the transport network, causing longer round trip time (RTT) for the user data correspondingly. Thus, for example, downloading times of Internet pages become longer as long RTT limits the data transfer speed of the TCP (transmission control protocol) protocol.
For example, in 3GPP, a “local breakout” has been understood as a U-plane Anchor selection from the visited PLMN rather than as a way of using a SAE Gateway from the home PLMN while roaming. In a known intra PLMN local breakout solution, route optimization is provided when the UE is moving far away from the current SAE Gateway. This is implemented by reselecting a new SAE Gateway when the UE moves to a new region and taking the new SAE Gateway and IP address in use after detecting inactivity in the old sessions and using the new local IP address for new sessions. Full relocation to a new SAE Gateway occurs when all old sessions are terminated. This solution aims to provide an optimized IP routing by moving the SAE Gateway in the core network closer to the UE while it moves within the PLMN. However, solutions are needed where a more local IP breakout gateway can be selected closer to the base stations for providing localized packet data services that could be used in parallel with the centralized packet data services in the public mobile networks. In this way the public mobile networks could also provide “local calls” instead of forcing all calls to be long distance calls.
In order to tightly integrate private “local breakout” cells into EUTRAN procedures, for example, the radio access network should be equipped with detailed procedures to handle the handover of private cells in E-UTRAN. Currently there is a need to determine how eNodeB can enable different handover decisions considering public and private cells. During the UE measurement reports in a dedicated mode, UE may report a Tracking Area (TA) and a cell ID of the neighbor cell. This information is not enough for eNodeB as it is not able to distinguish if the reported cell comes from a private cell or a public cell, unless different TA value ranges are used for public and private cells. Restricting the use of different tracking areas for private and public cells is however not desirable in order to avoid increasing the length of the TA to overcome capacity problems.